The invention relates to tube cutters, especially for plastic tubes, adapted to cut and bevel tubes.
Such a tube cutter is for example known from West German Gebruachsmuster 78 11 885. In this, arrangements are made to carry out the cutting operation by changing the position of the tool holder, which can be guided to give either a flat, radial cut face or a conical cut face. The latter is also frequently called a "bevel".
The known tube cutter has proved best however where the outer face of the tube to be cut is as close as possible to a mathematically exact cylinder. It is found in commercially available plastic tubes, however, that there are departures from the circular and/or in diameter. When a tube with a diameter too large by one or a few millimeters is stressed, the cross section inside the tool deforms to an oval, so that ultimately, in either case, a tube has to be cut of which the outer face departs more or less from an exact cylinder.
If one effects a severing cut with a bevel with the known tool, the lines between the conical surface (=bevel) and the end face formed by the cut on the one hand and the outer face on the other hand is wave-shaped, the bevel being most pronounced where the radius, from the nominal axis of the tube, is greatest. The user has, in consequence, the impression that the tool is not working properly. Furthermore, it is desired that bevels are as even as possible so that the bevelled part of the tube can be inserted into a coupling or the like with a sealing ring. Finally, however, the cutting process itself leads to difficulties because the residual section remaining at the end of the cutting process is irregular, so that the cutting tool at one position penetrates the inner face of the tube, while at another position it is still inside the material. The actuating forces required for a rotation of the known tool are as a result irregular; in thin-walled and/or brittle tubing, either the tool gets stuck or it does not generally make a clean cut.
It is an object of the invention to improve the above described tube cutter, so that it makes possible, even with tubes of which the outer surface departs from an exact cylinder, a simpler operation as well as a cleaner cut and especially a cleaner bevel.